Magnetic transducer



lllli FIG. 4

INVENTOR. EDWARD A. 00401:;

United States Patent MAGNETIC TRANSDUCER Edward A. Quade, San Jose, Calif., assignor to International Business Machines Corporation, New York, N. Y., a corporation of New York Application July 19, 1954, Serial No. 444,218

Claims. (Cl. 179-1003) The present invention relates generally to magnetic transducers.

In the compute: field, as well as in other allied fields, there is an ever increasing demand for movable recording heads which permit recording on or read-out from various portions of a record medium. Accordingly, it is one object of this invention to provide an improved, movable recording head.

To permit fast access times, i. e., to permit the recording head to be rapidly repositioned, it is desirable that the mass to be moved be as small as possible. It is, therefore, another object of this invention to provide a movable recording head having a very low mass.

Still another object of the invention is to provide a magnetic transducer which is simple and which is relatively inexpensive to fabricate.

A further object is to provide a novel transducer wherein the core thereof is movable relative to its winding.

Another object of this invention is to provide a trans ducer of small size to give access between closely spaced magnetic records such as rotating discs.

A still further object is to provide a low mass recording head adapted [O readily follow an irregular recording surface.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of example, the principle of the invention and the best mode which has been contemplated of applying that principle.

In the drawings:

Fig. 1 is a perspective view of the novel transducer disposed adjacent a recording medium.

Fig. 2 is an elevation taken along line 2-2 of Fig. 1.

Fig. 3 is a vertical section taken along line 3-3 of Fig. 2.

Fig. 4 is a vertical section taken along line 4-4 of Fig.2.

The transducer of the invention comprises a magnetic core (Fig. 2) of Mumetal or other suitable high permeability material slidably mounted on a winding 16. In the present embodiment, the core 15 consists of a small strip of Mumetal which is loosely wrapped around the winding 16, the adjacent ends of the strip being spaced apart a short distance to provide a non-magnetic gap 17 (Fig. 4) in the flux path around the core. It should be noted that the core may be constructed as above described or that it may be laminated, the particular construction to be used being dependent upon the existing operating conditions.

The winding 16 (Fig. 2) is but a single, endless turn of low resistance material, such as copper, of sufficient crosssectional area to conduct the current necessary to obtain satisfactory recording. Under the conditions set up experimentally, it was found that a current in the neighborhood of ten amperes was necessary for a satisfactory recording, a rectangular conductor .020 inch by .125 inch being utilized for this purpose. It should be mentioned in this connection that the optimum high frequency response of the transducer may be achieved by maintaining the induction of the winding 16 at a minimum. This is accomplished by spacing the oppositely disposed portions of the winding 16 as close to each other as is practicable, while maintaining sufficient clearance therebetween to permit unobstructed movement of the core 15 along the winding 16.

Current is induced in the single turn winding 16 by a transformer 18 which includes a multiturn winding 19 and a core 20, the winding 16 being linked to the core 20. It will be understood that the number of turns of the winding 19 is determined by the current available in the control structure with which it is to be associated. For example, if a control current in the neighborhood of .200 ampere is available, it is necessary that the winding 19 have approximately 50 turns to provide a current in the winding 16 of ten amperes.

In the use, the transducer is suitably supported to dispose the gap 17 of the core 15 closely adjacent the mag netic recording surface with which it is to be used. Referring to Figs. 1 and 2, it will be seen that the transducer is supported, by means not shown, in longitudinal alignment with the radius of a rotatable disc 21, the surface 22 of which is coated with a suitable magnetizable material, and when the coil 19 is energized, a spot on the disc 21 adjacent the gap 17 is magnetized. Conversely, when the disc 21 is rotated and when a magnetized spot on the disc 21 is moved past the core 15, a current is induced in the winding 19 which is utilized to effect read-out.

I t was mentioned earlier herein that the core 15 is slidably mounted on the winding 16, and it will be understood that the core may be adjustably positioned, in any convenient manner, along the radius of the disc 21 to permit information to be recorded on or taken from various, selected portions of the disc. Due to the very low mass of the core 15, it is clear that it may be repositioned very quickly, thus maintaining the access time at a minimum. Additionally, in some applications, such as where discs having runout are utilized as the record medium, it may be desired that the core 15 be arranged to follow the surface of the disc to permit a more uniform recording. As noted above, the core 15 is loosely wrapped on the winding 16, and is, therefore, readily adapted to follow the disc, the low mass of the core being extremely beneficial in this connection.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art, without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. A transducer for :coacting with a magnetic record member comprising an elongated winding extending parallel to the recording surface of said member and a core having mounting means for sliding said core along said winding to record or reproduce signals at difierent locations on said record member.

2. A transducer for coacting with a magnetic record member comprising an elongated, single-turn winding extending parallel with the recording surface of said member and a core slidably mounted upon said winding for movement there along to record or reproduce signals at different locations on said record member.

3. A transducer for coacting with a magnetic record member comprising an elongated winding extending parallel to and spaced from the recording surface of said mem her and a core having mounting means for sliding said 3 core along said winding to record or reproduce signals at different locations on said record member.

4. A transducer for coacting with a magnetic record member comprising an elongated, single-turn winding extending parallel with the recording surface of said member and a core embracing said winding and slidable there along to record or reproduce signals at different locations on said record member.

5. A transducer for coacting with a magnetic record member comprising an elongated winding extending parallel to the recording surface of said member and a core surrounding said winding having mounting means for sliding said core along said winding to record or reproduce signals at different locations on said record member.

References Cited in the file of this patent UNITED STATES PATENTS FOREIGN PATENTS Germany Apr. 25, 1935 

